Employing parathyroid gland slices and dispersed cells of bovine and procine origin, we are studying and comparing the rate of synthesis, the intracellular processing, packaging and secretion of several proteins of the gland. These proteins include the hormonal peptides proparathormone and parathormone, proteolytic enzymes, cathepsin B and plasminogen activator and the newly identified proteins ubiquitin and secretory protein-I. At the same time, we are validating the two-pool concept for parathormone and secretory protein-I secretion by physical localization or identification of the two pools and chemical characterization of the proteins and the membrane structures comprising these pools.